Device for grounded securing of an element at a hole in a metal plate

ABSTRACT

A device for grounded securing of an element (1) at a hole (9) in a metal plate (10) comprises members (6, 13) movable on both sides of the plate towards each other and the plate for securing the element to the plate and means (12) adapted to establish an electrical connection between the metal of the plate and the element, These means (12) are arranged to enter into radial abutment on the circumferential wall (27) of the hole while establishing said electrical connection.

FIELD OF THE INVENTION AND PRIOR ART

The present invention relates to a device for grounded securing of anelement at a hole in a metal plate.

Thus, to ground means here that the element in question is brought intoelectrical connection with the metal of the plate, in which the hole ismade. The invention relates to such grounded securing of all types ofelements, for which there is a desire to obtain such a securing, but thecase of an antenna securing element intended to be secured in the holein the body sheet of a car for a radio antenna, in particular for a cartelephone, will by way of example be discussed hereinafter.

For the good function of such an antenna, and also other elements of asimilar type, the resistance to ground, i.e. in this case the car sheet,of the antenna securing point has to be very low. Such a groundedsecuring of an antenna to the car sheet has until now been carried outby either exposing the metal plate or sheet on the inside of the car,i.e. most frequently on the underside of the car ceiling, around saidhole, so that the securing member located inside the car may enter intoelectrical contact generating abutment upon the metal plate andestablish an electrical connection therebetween and the antenna securingelement, or the car enamel may be removed from the surfaces surroundingthe hole and located on the outer side of the metal plate, so that thesecuring member externally located may come into an electric contactgenerating abutment upon these surfaces and thereby achieve anelectrical connection between the metal plate and said element. Themechanic has in the former case great difficulties, since he has toassume a very uncomfortable working position and often has to stretchhis arm about one meter and at the same time handle a tool to be rotatedand pulled upwardly. It may thereby easily happen that the result, i.e.the grounding, becomes imperfect. In the latter case it is, besidesrequirements of accuracy and patience during the mounting, a great riskfor damaging or in any case influencing the surrounding enamel, so thatmoisture later on penetrates thereunder and "roses" are created aroundthe antenna location followed by corrosion on the metal platethereunder.

BRIEF DESCRIPTION OF THE INVENTION

The object of the present invention is to provide a device of the typementioned in the introduction, which enables grounded securing of anelement at a hole in a metal plate, especially but not exclusively anantenna securing element at a hole in a car body sheet or plate, whichfinds a remedy to the inconveniences mentioned above of already knowndevices of this kind.

Thanks to the fact that said means are adapted to enter into radialabutment on the circumferential wall of the hole while establishing saidelectrical connection, it is not necessary to expose the metal of theplate neither on the inner side nor on the outer side thereof beforesecuring the element, and no other exposure of any portions of the metalplate are either required, since the metal surfaces of the plate alreadyexposed by producing the hole are used for obtaining the grounding aimedat. This means a greater simplicity as well as an improved result of themounting with respect to devices already known. When securing theelement to the plate it is only necessary to displace said means into agood radial contact with the circumferential wall of the hole and movethe securing members towards each other into the securing position forcompleting the mounting in a satisfying manner. With respect to the casediscussed above of mounting an antenna for a car telephone, the mountinggets much simplier, the risks for sheet damages caused by the mounting,for instance through corrosion, are eliminated and a very goodelectrical connection between the antenna securing element and the metalof the plate may be obtained with a high reliability.

According to a preferred embodiment of the invention said means compriseportions arranged to be displaced radially inside said hole intoabutment upon the circumferential wall of the hole. Said means maythereby by the portions in question easily be brought into the hole,since this may be accomplished with a certain clearance, whereupon theportions may be brought to move in a radial direction so as to obtainthe abutment required, so that the mounting work is very easy. Accordingto a further preferred embodiment of the invention said means arearranged to enter into said abutment by displacing the securing membersin the direction towards each other. Even this characteristiccontributes to simplifying the mounting work, and a combination of thisembodiment and the preceding one is particularly advantageous.

According to still a further preferred embodiment of the invention saidmeans are designed to enter into a preloaded abutment onto saidcircumferential wall. This is advantageously obtained according toanother advantageous embodiment of the invention by producing at leastportions of said means of a resilient material. A very good and reliableelectrical contact between said means and the metal of the plate may inthis way be continuously ensured.

Further advantages and advantageous characteristics of the inventionwill appear from the following description and the other dependentclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

With reference to the appended drawings, below follows a description ofa device according to a preferred embodiment of the invention cited asan example. In the drawings:

FIG. 1 is an exploded view of a preferred embodiment of the deviceaccording to the invention applied to an antenna, in particular for cartelephones,

FIG. 2 is a partially sectioned view of the device according to FIG. 2in a state in which it is secured at a hole in a metal plate, somehousing parts being broken away so as to improve the illustration,

FIG. 3 is an enlarged perspective view of a washer being a part of themeans of the device for establishing an electrical connection,

FIG. 4 is a partially sectioned view enlarged with respect to FIG. 2 ofthe device according to the invention in a state, in which the securingto a metal plate is still not completed, and

FIG. 5 is a view corresponding to FIG. 4 of the device in the state, inwhich said securing is completed.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

FIG. 1 shows an elongated element 1, on which an antenna radiator isintended to be secured and which is intended to be secured at a hole ina metal plate. The element 1 has an upper cylindrical thinner portion 2,which is electrically conductive and to the upper end of which anantenna radiator not shown is intended to be secured. The element 1 hasfurther an intermediate portion 3 of an electrically insulatingmaterial, such as plastic, and which has an intermediate thickness andis provided with chamferings 4 for holding it by a wrench or similartool, as well as a lower, electrically conductive, thicker portion 5.The definition of the upper and lower portions may of course be invertedshould the element be arranged with the portion here called the upperportion downwardly. The lower, thicker portion 5 is sleeve-like, and theintermediate portion 3 extends coaxially through the lower portion 5 tothe lower end thereof, and the corresponding circumstance is valid forthe upper portion 2, which extends coaxially in the intermediate portion3 to the lower end of the lower portion 5. Thus, the portions 2, 3 and 5function together as a coaxial cable, and the portion 2 alternatesbetween being the positive pole and the negative pole of the antennasecuring element 1, whereas the portion 5 is the ground part of thelatter element. The upper portion 2 has at both ends thereof an outerthread, and the lower portion has over the entire length thereof anouter thread. A first securing member 6 is rigidly secured to the end ofthe lower portion 5. This member is formed by a piece havingconsiderably greater dimension in at least a transversal direction withrespect to the extension of the element than the diameter of the hole atwhich the element 1 is intended to be secured. The securing member 6 hassurfaces 7 directed substantially parallelly to the center line of theelement 1 and intended to come into abutment upon those portions of ametal plate which surround the hole mentioned above. The securing member6 has also a channel 8 for introducing and attaching a suitable coaxialcable to the abovementioned coaxial cable formed by the element 1.

Reference is now also made to the other figures. The element 1 isintended to be secured at a hole 9 in the metal plate 10 whileestablishing an electrical connection between its lower portion orground portion 5 and the metal of the plate. For obtaining such securingthe element 1 is intended to from one side of the plate, in the case ofa car antenna from the interior of the car, be displaced through saidhole 9 until the surfaces 7 of the first securing member 6 come intoabutment upon surfaces of the metal plate 10 surrounding the hole 9.Through the elongated design of the member 6 this could also byinclining the element 1 be pushed through the hole 9 from the oppositedirection. Then, at the same time as or possibly even before theobtention of said abutment of the first securing member 6, an annularmeans 12 having an inner central opening 11, here in the form of anexpander washer, is threaded over the element 1 into the position shownin FIG. 4, in which it surrounds the lower portion 5 of the element. Theconstruction of this annular means 12 will be described more in detailfurther on. A second securing member 13 in the form of a nut having aninner thread corresponding to the outer thread of the lower portion 5 isthen screwed onto said lower portion 5, so that the two securing members6 and 13 approach each other from both sides of the metal plate 10 so asto secure the element 1, i.e. indirectly the antenna, with respect tothe metal plate. The annular means 12 will then function as an insertbetween the nut 13 and the metal plate 10, which appears from FIG. 2.With reference made in particular to FIG. 3-5 it will be explainedfurther on how the nut 13 co-operates with the annular means 12 forsecuring the antenna securing element with respect to the plate whileobtaining the grounding of the portion 5 required.

When grounded securing of the element 1 at the metal plate 10 has beenobtained, a perforated protection cap 14 is brought over the element 1,so that it by lower surrounding support portions 15 comes to bear uponthe metal plate 10, whereupon a nut 16 is brought onto the element 1 andtightened with respect thereto at the lower thread of the upper portionso as to achieve a tight bearing of the support portions 15 of theprotection cap 14 against the metal plate 10 so as to prevent dirt,moisture and the like from penetrating into the interior of theprotection cap 14 and thereby through the hole 9 reach the interior ofthe car. A further protection cap 17 is then screwed above the nut 16onto the element 1 through the upper thread thereof, whereupon themounting is completed and the state according to FIG. 2 is obtained.

How the grounding, i.e. the electrical connection between the metal ofthe metal plate and the element is obtained in connection with thesecuring will now be described with reference to FIGS. 3-5. The annularmeans 12 is made of a material having a good electrical conductivity.The annular means 12 is further so selected and so machined,respectively, that it is resilient, i.e. it stores potential energy upondeformation from an unstressed rest state, and it tends to use saidenergy so as to return to the initial rest position. The annular meanshas a conical portion 18, which extends from the outer edge 19 of thering and to the central opening 11 and is intended to be directed in thedirection towards the second securing member 13 (see the positionaccording to FIG. 4) in the state in which it is applied around theelement 1. With respect to the axis of the opening substantially axialfirst portions 20 in the form of an annular flange project from theconical annular portion in the direction of the first securing member 6.Substantially axial second portions 21 in the form of a second annularflange project from the conical portion 18 in the region of the outeredge 19 of the annular means 12 substantially parallelly to the firstannular flange. The two annular flanges 20 and 21 are concentric withrespect to the center axis of the central opening 11. The outer diameterof the first annular flange 20 is selected to be somewhat smaller thanthe diameter of the hole 9 in the metal plate 10, so that this annularflange may easily be introduced into said hole 9, whereas the outerdiameter of the annular flange 21 is so selected that this annularflange will come into abutment on portions of the metal plate 10directed axially with respect to the center axis of the hole andsurrounding the hole when the annular means 12 is moved towards saidhole 9. The annular flange 20 projects in the axial direction furtherthan the annular flange 21, so that the former enters at least a bitinto the hole 9 before the latter comes to bear against the metal plate.

A material saving or cut-out 22 extending substantially axially inthe-direction of the cone surface of the conical portion is carried outbetween said first and second annular flanges 20, 21. Furthermore, slits23 extending radially from said central opening 11 and distributed withthe same angular space around the opening are arranged, which extendthrough the first flange ring 20 and divide this into a plurality, inthe case shown eight, sections 24.

The function of the device just described, in particular with respect tothe co-operation between the securing member 13 and the annular means 12is as follows: the first 6 and the second 13 securing member are uponreaching the position according to FIG. 4 displaced towards each otherby turning the nut 13 in the tightening direction. When the surface 20of the first securing member 6 enters into contact with the metal plateand the nut 13 by the axially directed surface portions 25 thereof atthe same time has entered into contact with the inner edge 26 of theconical portion 18 and the outer annular flange 21 bears against themetal plate 10, continued tightening of the nut 13 will causesuccessively flattening of the conical portion 18 while applying axialforces to the inner edge 26 thereof, whereby these forces aretransferred to a substantially radially directed movement of the annularflange sections 24, so that these come into abutment onto thecircumferential wall 27 of the hole 9. The material saving 22 as well asthe slits 23 facilitate the radial movement of the first annular flange20, so that this can take place without any substantial deformation ofthe second annular flange 21. It is also of importance that the diameterof the opening 11 in the means 12 is somewhat greater than that of thelower portion 5 of the element. The tightening of the nut 13 ispreferably continued until the position shown in FIG. 5 is reached, inwhich the conical portion 18, which initially makes an angle of about85° with the center axis of the hole, has been completely flattened, sothat this angle has become 90°. Thanks to the resiliency of the materialforming the annular means 12 the radially directed parts of the annularflange 20 will bear under a preload against the circumferential wall 27,so that a very good and reliable contact is obtained between the annularflange 20 and the metal of the metal plate 10 exposed by thecircumferential wall 27. In absence of said circumferential wall 27 thefirst annular flange 20 would in this position certainly move a littlebit further in the radial direction.

The electrical connection between the element 1, i.e. the antennasecuring element, and the metal of the metal plate, thus the groundingof the antenna securing element with respect to the metal plate, is hereobtained by the radial abutment of the annular flange 20 of the annularmeans 12 on the circumferential wall 27 of the hole, the axial abutmentof the annular means 12 on the nut 13 and the thread engagement thereofwith the ground part or portion 5. The resiliency of the annular means12 will then also give rise to a preloaded abutment of the portion 18conical in the unloaded state of said means on the axial surfaceportions 25 of the nut 13. In the particular case of an antenna for acar telephone the resistance between the antenna and the ground, i.e.the body sheet of the car, may not exceed 0,4 Ohm, and this criterion iseasily fulfilled by the device according to the invention.

It appears from FIGS. 1, 4 and 5 that the first securing member 6 has acountersink 28 around the lower portion 5 of the element. Thiscountersink is arranged to enable the use of the device according to theinvention for securing at holes in metal plates of varying thicknesses,so that in the case of a thinner metal plate than the one shown in thefigures the first annular flange 20 will in the position according toFIGS. 2 and 5 project somewhat into said countersink 28.

The patent claim definition "displaced radially" comprises all types ofmovements having a radial direction component, so that it is thenpossible that the movement has also an axial direction component. Thesame discussion is valid for the definition "radial abutment", whichaccordingly means that the abutment takes place in a direction having aradial component.

The invention is of course not in any way restricted to the preferredembodiments described above, but several possibilities to modificationsthereof would be apparent to a man skilled in the art, without departingfrom the basic idea of the invention.

It would for example be well possible to almost arbitrarily change theshapes of the cross section of the hole, the element and also the meansfor obtaining the electrical connection between the plate and theelement. Although a round cross section shape seems to be most suitable,especially for achieving a symmetrical force distribution, it would bewell possible to provide the hole with a cross section being triangular,rectangular or shaping it in another way if desired.

The means could be designed to be influenced in radial direction by anaxial action of the second securing member in another way than byproviding a conical portion of the means, for example by providingmutually co-operating wedge surfaces on on one hand the securing memberand on the other the annular member, wherein the wedge-shaped member ofthe securing means would then be regarded as a part of said means.

It would of course be well possible to arrange said means establishingan electrical connection on the same side of the metal plate as thefirst immobile securing member. It would also be well possible toarrange both securing members movable with respect to the element,wherein such a movement does not necessarily have to be dependent on aturning movement with respect to a thread, but also other tighteningdevices than a thread engagement would be conceivable.

I claim:
 1. A device for grounded securing of an element (1) at a hole(9) in a metal plate (10) comprising:members (6, 13) movable on bothsides of the plate towards each other and the plate for securing theelement to the plate and means (12) adapted to establish an electricalconnection between the metal plate and the element, said means (12)being arranged to enter into radial abutment on the circumferential wall(27) of the hole while establishing said electrical connection, saidmeans (12) comprising at least one flange portion (20) arranged to bedisplaced radially outwardly within said hole (9) into abutment on thecircumferential wall (27) of the hole; wherein said means (12) arearranged to enter into said abutment for electrical contact by saidmoving of the seeming means (6, 13) in a direction towards each other.2. A device according to claim 1 wherein said means (12) are adapted toenter into a preloaded abutment onto said circumferential wall (27). 3.A device according to claim 2 wherein at least a part of said means (12)is deformable from an initial shape in an unstressed state into adeformed shape while storing potential energy on establishing saidabutment.
 4. A device according to claim 3 wherein at least a part ofsaid means (12) is made of resilient material.
 5. A device according toclaim 1 wherein said means (12) is adapted, upon moving the securingmembers (6, 13) towards each other, to be urged by at least one (13) ofsaid members in the axial direction of the hole (9) and thus causeradial displacement of said flange portion (20) of the means (12)located in the hole.
 6. A device according to claim 1 wherein said means(12) comprises a ring having a central opening (11) for receiving aportion of the element (1).
 7. A device according to claim 1 furthercomprising an externally threaded member (5) arranged to be pushed intosaid hole (9) of the plate (10), and that one of the securing members(13) is a nut for receiving said threaded member and turnabletherearound for said securing.
 8. A device according to claim 1 whereinsaid means (12) are arranged to establish said electrical connection byinterposedly bearing against the metal plate (10) and one of thesecuring members (13) so as to establish an electrical connectionbetween said means (12) and the element (1).
 9. A device according toclaim 1 wherein the element (1) is arranged to receive an antenna forreceiving radio waves.
 10. A device according to claim 1 wherein theplate (10) is a body panel of a car.
 11. A device according to claim 1the element (1) includes a mounting piece connected thereto and themeans (12) comprises a ring having a central opening (11) therein forreceiving the mounting piece.
 12. A device for grounded securing of anelement (1) at a hole (9) in a metal plate (10) comprising:members (6,13) movable on both sides of the plate towards each other and the platefor securing the element to the plate; means (12) adapted to establishan electrical connection between the metal plate and the element, saidmeans (12) being arranged to enter into radial abutment on thecircumferential wall (27) of the hole while establishing said electricalconnection, said means (12) comprising at least one flange portion (20)arranged to be displaced radially within said hole (9) into abutment onthe circumferential wall (27) of the hole; said means (12) is adapted,upon moving the securing members (6, 13) towards each other, to be urgedby at least one (13) of said members in the axial direction of the hole(9) and thus cause radial displacement of one of said flange portion(20) of the means (12) located in the hole; said means (12) comprising aportion (18) being conical in an unloaded state and adapted to bearranged coaxially with respect to the hole (9) of the plate (10), theconcical portion (18) is provided with a central opening (11) at the tipthereof and converges from the hole of the plate towards said onesecuring member (13); the at least one flange portion including asubstantially axial first flange portion (20) integral with the conicalportion and projecting into the hole of the plate and a second flangeportion (21) facing the plate adjacent said hole, and that the means isarranged, upon moving said one securing member (13) towards the plate,by bearing against the conical portion (18) adjacent the central opening(11), to press said second portion (21) into abutment upon the plate(10) and by continued pressing causing the first flange (20) to bedisplaced radially in the hole and into abutment upon thecircumferential wall (27) thereof by at least partially flattening theconical portion (18).
 13. A device according to claim 12 wherein thecone surface of the conical portion makes an angle greater than 80°,with the center axis of the hole.
 14. A device according to claim 13wherein the cone surface of the conical portion makes an angle betweenapproximately 83°-87° with the center axis of the hole.
 15. A deviceaccording to claim 12 wherein the means (12) comprises first and secondflange portions and a recess (22) formed between said first (20) andsecond (21) flange portions and extending substantially axially in thedirection of the cone surface of the conical portion.
 16. A deviceaccording to claim 12, wherein said first and second flange portionsinclude a first and a second annular flange (20, 21) concentric withrespect to each other and to the hole, wherein in the unloaded state ofsaid means the outer diameter of the first annular flange (20) is atleast as large as the hole.
 17. A device according to claim 12 wherein aplurality of slits (21) extend from said central opening (11) outwardlyinto the conical portion (18) so as to divide the conical portion into aplurality of sections (24) around the central opening.
 18. A deviceaccording to claim 17 wherein the slits (23) extend into and through thefirst flange portion (20) for dividing the first flange portion into aplurality of sections (24) around the central opening (11).
 19. A deviceaccording to claim 17 wherein the slits (23) extend radially and areuniformly distributed around the central opening (11).